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Precious Metals

Precious metals are engineering materials first and stores of value second. Silver is the best electrical and thermal conductor there is; gold does not tarnish, so a gold contact still conducts after twenty years in a drawer; platinum survives molten glass and red-hot acid and is the reference for laboratory crucibles and thermocouples; palladium absorbs hydrogen and catalyzes almost everything. In jewelry and dental work they are chosen for color, hypoallergenicity and permanence. The metal price dominates every part, so they are used as thin plating, small components or where nothing else will do.

Precious metals by element

Gold alloys24K pure · 18K (75 %) · 14K (58 %) with Ag, Cu, Pd, Ni3330 – 650Contacts, bond wire and connector plating (pure or hard gold), dental restorations, jewelry and watch cases. Pure gold never tarnishes and is very soft; 18K and 14K add hardness and colour (yellow, white, rose).
Silver alloysFine 999 · Sterling 925 (Cu) · Argentium8640 – 420Electrical contacts, switchgear and relay parts, bus-bar plating, brazing alloys, mirrors and reflectors, jewelry and tableware — the highest conductivity of any metal; sterling adds hardness for wear.
Platinum alloysPt 950 (Ru, Ir, Co) · Pt-10Rh · Pt-30Rh1845 – 850Laboratory crucibles and dishes, glass-fibre bushings and stirrers, thermocouples (Type R, S, B), electrodes, catalytic and medical electrodes, pacemaker and implant components, fine jewelry — inert to 1,700 °C and to most acids, dense and ductile.
Palladium alloysPd 950 · Pd-Ag · Pd-Cu1355 – 380Dental alloys, white-gold whitener, hydrogen purification membranes, multilayer capacitor electrodes, low-cost platinum substitute in jewelry and contacts — lighter and cheaper than platinum with similar chemistry.
Other precious metalsVarious4170 – 245Brazing fillers, solders and specialty alloys outside the groups above.

Choose a precious metal for

Electrical contacts, connectors, slip rings and bond wires where the surface must stay conductive without tarnish (gold, silver, Pd alloys); laboratory crucibles, electrodes, thermocouples and glass-melting hardware (platinum, Pt-Rh, Pt-Ir); dental crowns, inlays and implant components (gold and Pd alloys); jewelry and watch cases; brazing filler metals; mirrors and IR reflectors (gold, silver); and catalysts, sensors and hydrogen-purification membranes (Pd, Pt).

Look elsewhere when

The property can be delivered as a plating or clad layer on a base metal — which is almost always (gold flash on brass or copper contacts, silver-plated bus bar, Pt-clad titanium anodes); strength or hardness matters (all precious metals are soft; even hard 14K gold is weaker than mild steel); the part is large or bulk-loaded (the metal cost dwarfs the machining cost); or a copper alloy, rhodium-plated brass or stainless meets the conductivity or corrosion requirement. Silver tarnishes in sulfur-bearing air, and gold above 18K scratches easily.

Yield strength against electrical conductivity, every precious metal grade

No materials in view have both of these properties.

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Precious Metal by application

Electrical contacts and conductors
Fine silver for the lowest resistance and for relay and switch contacts; hard gold plating where the contact must stay clean at low voltage for decades; Pd-Ag as the cheaper alternative in connectors and hybrid circuits.
Jewelry and watch components
Cast, CNC-machined or hand-finished; 18K for colour and value, 14K for hardness and price, Pt 950 for permanence and hypoallergenic settings, sterling for volume pieces.
Dental and medical
High-noble gold and palladium alloys for crowns, inlays and frameworks (biocompatible, castable, bondable to porcelain); Pt-Ir for pacemaker electrodes and marker bands.
Mirrors, reflectors and optics
Gold for infrared reflectors and thermal-control coatings (99 % IR reflectance, no tarnish); silver for the highest visible reflectance where it can be protected.

Manufacturing notes

Casting
Investment (lost-wax) casting from 3D-printed or CNC-milled patterns is the standard route for jewelry, dental and small precision parts in gold, silver, platinum and palladium alloys — near-net shape with minimal scrap, which matters when the scrap is worth more than the labour.
CNC machining
Precious metals are soft and gummy: sharp, polished tools, high speed, light cuts and full chip recovery — every gram of swarf is weighed and refined. Sterling, 14K gold and Pt 950 machine reasonably; fine silver and pure gold smear. Parts are typically machined slightly oversize and finished by hand polishing.
Plating and cladding
Most engineering uses of precious metals are 0.1–5 µm electroplated or a few microns clad onto copper, brass, nickel or titanium: hard gold (Au-Co) on connectors, silver on bus bar and RF parts, rhodium on white gold and contacts, Pt on titanium anodes. Specify thickness, underplate (nickel barrier) and hardness, not just "gold plated".
Joining
Hard soldering and brazing with matched-karat or silver-alloy fillers; laser welding for jewelry repair, dental frameworks and platinum; resistance welding for contacts; wire bonding for gold and Pd bond wire. Fusion welding of pure silver and gold is straightforward; Pt alloys weld cleanly under argon.
Finishing and assay
Polishing to mirror, rhodium flash for white finishes, anti-tarnish passivation for silver, hallmarking and assay certification on request. Every job is tracked by weight in and out; scrap and polishing residue are returned or credited.

Precious Metal — frequently asked

Why plate gold onto contacts instead of using another metal?

Gold is the only common conductor that forms no oxide or sulfide film at all, so a gold-to-gold contact has the same low resistance after years in the air as on day one — critical at signal-level voltages that cannot punch through a tarnish layer. A hard-gold plating of 0.5–1.5 µm over a nickel barrier on a copper-alloy spring gives that surface at a tiny fraction of the cost of a solid part. Silver conducts better but tarnishes; tin and nickel oxidize.

What is the difference between 24K, 18K and 14K gold?

Purity. 24K is 99.9 % gold — softest, deepest yellow, never tarnishes, used for contacts, bond wire and bullion. 18K is 75 % gold with silver, copper, palladium or nickel added for hardness and colour — the fine-jewelry and dental standard. 14K is 58.5 % gold, harder and cheaper still, the everyday jewelry alloy in North America. Hardness roughly doubles from 24K to 14K; corrosion resistance falls only slightly.

Platinum or palladium?

Chemically they are cousins: both inert, both white, both hypoallergenic. Platinum is denser (21.4 vs 12 g/cm³), higher melting, and the choice for laboratory ware, thermocouples, electrodes and prestige jewelry. Palladium is lighter and usually cheaper, absorbs hydrogen (useful in purifiers, a nuisance in vacuum), and is the standard whitener in white gold and the base of most dental alloys. A palladium ring weighs half a platinum one.

Does sterling silver tarnish, and can that be prevented?

Yes — the copper in sterling and the silver itself react with sulfur in the air to form a dark sulfide. Anti-tarnish passivation, lacquer, rhodium plating, or Argentium (germanium-bearing) silver slow it dramatically; for electrical contacts a thin gold flash over the silver is the usual solution. Fine silver 999 tarnishes more slowly than sterling but is too soft for most wear parts.

How do you handle the metal value on a machining job?

By weight. Customer-supplied or purchased metal is weighed in, every chip, offcut and polishing residue is recovered, and the total is weighed out against the finished parts. Scrap is returned, refined or credited at the day's fix. Design for minimal stock removal — casting to near-net shape or starting from wire and sheet — because a machining allowance on a precious metal is real money.